1. Field of the Invention
The present invention relates to a blanking shear machine, and, more particularly, to a blanking shear machine having an upper turret provided with a holder for an upper blade and lower turret provided with a holder for a lower blade.
2. Description of the Related Art
Conventionally, in a blanking shear machine an upper blade formed on two contiguous sides with right angles therebetween mates with a corresponding lower blade, and, in one action, cuts two sides of a plate. The two sides with right angles therebetween clamp a workpiece in the form of a plate between the upper and lower blades, are made to agree in the X-axis and Y-axis directions of a numerically controlled positioning device, and then are secured so that they cannot rotate.
Accordingly, in the case where shearing is performed to a length longer than the length of one of the two sides right angles therebetween, the shearing by the blade is conducted such that the highest side of the punch blade is at one edge which is remote from the right angles, and the lowest part is at the remaining edge with the right angled section at a middle height, whereby a long linear shearing is performed, by repeating the shearing by one side of the blade. Accordingly, the overall size of the device must be very large, which is inconvenient.
In addition, in cutting out a comparatively large section in the center of a standard-sized plate to obtain a frame-shaped product, because the phenomenon by which the part which is cutaway by the shearing is pushed down is unavoidable, during the operation the plate work must be rotated with the clamp repositioned, which is inconvenient.